1. Field of the Invention
The present invention relates to a connector, and particularly to a connector which provides a fixing projection for a locking arm of a connector housing, and fixes the fixing projection in the mating connector by causing this locking arm to deform elastically, thereby to lock in the mating connector.
2. Related Art
In connectors, there is a connector so constructed that a locking arm is provided on an outer surface, and a fixing projection of the locking arm is fixed to the mating connector when the connector is inserted into the mating connector as shown in Unexamined Japanese Patent Publication 2001-68214.
In the connector of the above reference, as shown in FIG. 5, a locking arm 102 is formed integrally on an outer surface 101 of a connector housing 100.
This locking arm 102 is formed by raising a base end portion 103 from the outer surface 101 of the connector housing 100, and extending a cantilevered arm portion 105 from an end portion 103A of this base end portion 103 along the outer surface 101 of the connector housing 101. In this arm portion 105, a fixing projection 106 is formed.
This connector is inserted into the mating connector (not shown), whereby the arm portion 105 comes into contact with the mating connector. As the arm portion 105 is deformed elastically in the direction of an arrow, it is put in the state shown by solid lines of FIG. 6.
When the fixing projection 106 of the arm portion 105 reaches a hood portion of the mating connector, the arm portion 105 is subjected to elastic restoration and put in the state shown by imaginary lines of FIG. 6.
The fixing projection 106 fixes to the hood portion of the mating connector, whereby the connector is locked in the mating connector in an engaged state.
It is thought that this connector, though it is formed of non-tempered glass under the existing circumstances, is formed of glass reinforced material that is low in the unit cost of material in order to hold the cost.
However, the glass reinforced material is, than the non-reinforced material, higher in bending elastic modulus and lower in allowable distortion.
Therefore, in case that the connector is manufactured with the glass reinforced material, there is fear that the locking arm 102 is easy to bend.
Here, elastic deformation of the arm portion 105 constituting the locking arm 102 will be described with reference to FIG. 7.
The arm portion 105 has a cantilevered support structure in which the base end portion 103 is a fulcrum, and the end portion, that is, the fixing projection 106 is a free end. Of the arm portion 105, the shape from the base end portion 103 to the fixing projection 106 can be shown as shown in FIG. 7.
Displacement δ of the fixing projection 106 is expressed byδ=PL3/(3EI)  (1),
Wherein P is reaction force of the arm portion 105, L is a length of the arm portion 105, E is a Young's modulus, I is a moment of inertia of area (I=bt2/12), b is a width of the arm portion 105, and t is a thickness of the arm portion 105.Stress σ is expressed by σ=M/Z  (2),wherein M is a bending moment (M=PL), and Z is section modulus of the arm portion 105 (Z=bt2/6).
From the expressions (1) and (2), the following expression is formed:σ=3Etδ/(2L2)  (3)
From the expression (2), the following expression is formed:P=bt2/(6Lσ)  (4)
From the expressions (3) and (4), it is found that when the thickness t of the arm portion 105 is reduced the reaction force P of the arm portion 105 becomes small.
Therefore, when the arm portion 105 is made difficult to bend by reducing the thickness t of the arm portion 105, the reaction force P of the arm portion 105 becomes small.
In case that the reaction power P of the arm portion 105 becomes small, there is fear that when the connector is engaged with the mating connector, engagement feeling becomes bad.
As a method of improving this engagement feeling, it is thought that the width b of the arm portion 105 is made large.
However, in case that the width b of the arm portion 105 is made large, when the connector is engaged with the mating connector, clearance for engagement with the mating connector cannot be secured.
Further, as another measure, it is thought that the position of the fixing projection 106 of the arm portion 105 is moved to an end portion 102A side of the locking arm 102 thereby to make the length L from the base end portion 103 to the fixing projection 106 large.
By making the length L from the base end portion 103 to the fixing projection 106 large, it is possible to make the arm portion 105 difficult to bend.
However, in case that the length L of the arm portion 105 from the base end portion 103 to the fixing projection 106 is made large, there is fear that the fixing projection 106 cannot fix in the mating connector.